Corrosion protection of waterborne epoxy coatings containing mussel-inspired adhesive polymers based on polyaspartamide derivatives on carbon steel

A novel mussel-inspired adhesive polymer (PHEA-DOPA) containing the 3,4-dihydroxyphenylalanine (DOPA) functional group based on polyaspartamide derivatives was synthesized. The corrosion protection of the waterborne epoxy coatings containing the adhesive polymers was investigated by electrochemical impedance spectroscopy (EIS). The results indicated that the PHEA-DOPA could improve the corrosion resistance of the waterborne epoxy coating. The corrosion products were also analyzed by Raman microspectroscopy (RM), indicating the formation of the insoluble DOPA-Fe complexes on the carbon steel surface. These complexes simultaneously acting as a passivating layer, can inhibit the process of corrosion at the metal-solution interface. The differential scanning calorimeter (DSC) measurement indicated that PHEA-DOPA can increase the crosslinking density of coating. The effect of O₂ on the protective mechanism of the PHEA-DOPA coating in a 3.5% NaCl solution was also evaluated by EIS. The results indicated that the barrier effect was significantly improved under aerated conditions because DOPA was oxidized to DOPA–quinone (Dq) by O₂, which triggered the reaction with Fe ions that were released from the surface of the carbon steel. This led to more compact coatings.     

仿贻贝粘附蛋白聚合物的合成及其防腐机理研究

目的合成水性含多巴胺功能基团的仿贻贝粘附蛋白聚合物(PHEA-DOPA),研究在水性环氧涂层中的腐蚀防护机理。方法通过聚琥珀酰亚胺与乙醇胺和多巴胺的连续氨解反应,成功制备了PHEA-DOPA粘附聚合物,并用红外光谱(FTIR)仪、核磁(1HNMR)共振波谱仪和紫外-可见分光光度计对其结构进行了表征。通过电化学阻抗谱(EIS)、扫描电子显微镜(SEM)、石英晶体微天平(QCM-D)和拉曼光谱,对含有PHEA-DOPA的水性环氧涂层在碳钢表面的防护性能与机理进行了研究。结果红外光谱、核磁光谱和紫外-可见光谱结果表明,成功合成了PHEA-DOPA聚合物。EIS和SEM结果表明,PHEA-DOPA的加入能够明显提高涂层的防护性能。QCM-D和拉曼光谱结果表明PHEA-DOPA的防腐机理为:PHEA-DOPA结构中的DOPA基团与Fe离子有较强的吸附络合作用,并在碳钢表面和涂层内部反应生成不溶性的[Fe(DOPA)3]3+络合物,可抑制铁的溶解过程,提高涂层的致密性。结论 PHEA-DOPA粘附聚合物的加入能够明显提高涂层的防护性能。